The present invention relates to engine cooling systems and in particular to cooling systems for internal combustion engines.
In conventional internal combustion engines coolant is fed to the engine block at the front and passes to the cylinder head via transfer holes associated with each of the cylinders. These transfer holes must be correctly sized, in order to achieve even cooling throughout the engine. In such systems, the coolant normally exits at the front of the cylinder head and consequently, coolant velocities at the rear of the cylinder head will be less than those at the front, since coolant will collect towards the front of the engine. To effectively control component temperature, coolant should be directed towards the areas which experience the greatest heat flow. These are, for a four valve per cylinder pent roof engine, the spark plug region and exhaust and inlet valve bridges. Thus, for conventional cooling, the lower flow rates at the rear of the cylinder head have to be catered for without compromising other cooling effects such as delivery of coolant between the exhaust valve bridge from the transfer holes.
In such systems, a cross flow technique is normally used in which portions of the coolant flow are directed separately to each cylinder. Consequently, in order to control component temperatures using coolant velocity, either a large overall flow rate or very small passage sizes need to be employed. There are restraints on the size of pump that may be used to circulate the coolant and consequently it is desirable that small coolant passage sizes should be used. Such small size passages have however to be cast or machined, neither of which are desirable in terms of water jacket core rigidity or cost.
The present invention overcomes these problems by directing the full flow of coolant from end to end along the cylinder head to cool all the cylinders.